GB544323A - Herringbone gear finishing - Google Patents

Abstract

544,323. Herringbone gears. NATIONAL BROACH & MACHINE CO. Feb. 11, 1941, No. 1876. Convention date, March 25, 1940. [Class. 80 (i)] [Also in Group XXII] In finishing herring bone gears, the gears are provided with point-crotch clearance and material removed by a shaving operation for a distance extending inwardly from the outer ends of the teeth. In one form, Fig. 1, taper teeth are first formed in a shaper operation so that there is a point-crotch clearance P.C. of 0.002 inches. The gear is then run with one half G in mesh with a conjugate gear like shaving tool T, arranged in crossed axis relationship the shaving being continued to a point 22 adjacent the crotch so that a pair of finished gears mesh as shown in Fig. 2 and the crotch clearance is reduced. In some cases a crowned form may be imparted to the teeth by oscillating the cutter about the common normal to the gear and cutter axes to obtain teeth which engage in the manner shown in Fig. 3. Or the crowning may be produced by rocking about an axis transverse to the gear axis and lying in a plane parallel to the gear and cutter axes. The contact is then confined to the regions 32 of the two parts of the gear. In another modification Fig 4 non- modified teeth may be shaved by means of a modified cutter which has the corners 42 of its teeth removed the cutter being oscillated about the common normal of the gear and cutter (centre 43) so that it removes metal from the point side at the other end. If desired the oscillation may also be carried in the other direction. The centre 43 may be shifted to vary the amount of metal removed from the respective tooth surfaces. In another modification the teeth may be first cut to different leads, Fig. 9, and then the teeth 91 shaved to relieve the points 92 and to remove metal from the outside corners on the crotch side. If desired only one member of a mating pair may be finished and the effect of crowning obtained.